Label-Free Analysis of Urine Samples with In-Flow Digital Holographic Microscopy

Area of Science:

• Medical diagnostics
• Microscopy techniques
• Infectious disease screening

Background:

• Urinary tract infections (UTIs) are common, necessitating extensive urine sample screening.
• Current urine culture plate tests (CPTs) often yield negative results, highlighting the need for rapid preliminary screening methods.
• A fast, simple technique is required to efficiently identify negative urine samples, reducing unnecessary laboratory workload.

Purpose of the Study:

• To propose and evaluate digital holographic microscopy (DHM) as a rapid screening tool for urine samples.
• To assess DHM's ability to identify and quantify cellular components and particles in fresh urine.
• To compare the diagnostic performance of DHM against established methods like urine culture plate tests (CPTs) and urine flow cytometry (UFC).

Main Methods:

• A digital holographic microscopy (DHM) system was used to analyze fresh urine samples in a glass capillary over 3 minutes.
• Holograms were recorded at 2 frames per second, followed by digital reconstruction to identify and count bacteria, blood cells, epithelial cells, and crystals.
• 180 urine samples were processed, with results compared against CPTs and urine flow cytometry (UFC) using standard evaluation metrics.

Main Results:

• DHM successfully identified and quantified various cellular components and particles in urine samples.
• The performance of DHM in classifying samples as negative or positive was similar to that of urine flow cytometry (UFC).
• DHM demonstrated comparable accuracy to UFC when using CPTs as the reference standard.

Conclusions:

• Digital holographic microscopy (DHM) is a suitable and fast screening technique for urine samples.
• DHM offers advantages such as being label-free and requiring no sample preparation.
• The digital recording of phase and amplitude images by DHM allows for potential further investigations.